Manufacture of sheet steel



Patented Oct. 15, 1935 MANUFACTURE OF SHEET STEEL Albert T. Reichenbach, Pittsburgh, Pa.

N Drawing. Application March 6, 1934, Serial No. 714,357

9 Claims.

This invention relates to the manufacture of steel in the form of thin sheets, such as sheet and tin plate, one of the objects being toproduce sound, smooth surfaces. Other objects may be inferred.

A characteristic feature of this invention is that the sheets are rolled from rimmed steel to a thickness of 26 gage or less. I-Ieretofore, rimmed steel has been rolled into sheets, but this has always 10 been confined to the thicker gages, such as 26 gage and heavier. The reason that ithas never been rolled into thin sheets is thatit has been impossible to open sheet-packs hot-rolled from such steel.

Before going further, it might be best to mention that rimmed steels are those steels which are not fully deoxidized before they are teemed into the ingot molds, the practice being to regulate the deoxidizing so that a controlled effervescing action takes place in the molds. This action is caused by the evolution of certain gases, and the mechanical stirring action of this evolution allows solidification of the steel to proceed more nearly in accordance with the natural laws governing the selective freezing of solutions. This results in skins or rims of metal adjacent the surfaces of the molds, which are lower in some of the metalloids than the steel forming the cores of the ingots.

Furthermore, this outside layer is freer from injurious surface defects than would be the case if the steel was fully deoxidized so that no effervescing action took place in the ingots.

The usual method of rolling any steel into sheets is to hot-roll ingots into sheet bars, and then to reheat these sheet bars and roll them to gage. This final rolling is done by arranging the sheets to form packs. The thinner the sheets must be the more sheets there are to one of these packs. In addition, the sheets must be subjected to further reheating. It is obvious that the thinner the sheets, the harder it is to open the sheetpacks, since these packs then consist of a greater number of sheets which have received a greater amount of working and a greater number of reheatings.

Rimmed steel can be rolled into sheets of relatively thick gages for the reason that there are a relatively few sheets to a pack and these sheets have not received very much working. Such sheets are known to have much finer and sounder surfaces than is ordinarily the case with sheets rolled from killed or fully deoxidized steels. This indicates that it is desirable to roll all sheets from rimmed steel regardless of their gage. However, in attempts heretofore made to roll such steel to the thinner gages, it has been found impossible to open the sheet-packs. It is obvious that if the sheet-packs cannot be opened, such attempts are failures. 5

For the reasons already explained, it is apparent that a steel that has any tendency to stick or weld together when rolled the fewer times necessary to produce the thicker gages, cannot be handled at all when it must be rolled the great- 101 er number of times necessary for the thinner gages. Such is the case with the steel being discussed. Experience and tests have shown that the dividing line between success and failure in the rolling of rimmed steel is a thickness of 15:

about 26 gage. So far as is known, no sheets of this steel have even been rolled thinner than this.

The present inventor has found that the opening of sheet-packs hot-rolled from rimmed steel may be facilitated by the addition of small per- 20 centages of nickel and/or chromium to the steel. This must obviously be made while the steel is in a molten condition. So far as is known, there has never been a rimming or efferverscing steel containing small percentages of nickel and/or chro- 25 mium produced by the deliberate addition of these elements. It has been found that steels containing either or both of these two metals may be rolled to any of the thinner gages by the usual method of hot-rolling the sheets in packs. 30 There is no usual difiiculty experienced in opening these sheet-packs otherwise than may be expected in connection with the use of ordinary steels containing the usual additions of phosphorus or silicon. 35 Tests have indicated that the best results are obtained from a rimmed steel containing from 0.05 to 0,15 per cent nickel and/or from 0.02 to 0.10 per cent chromium. They apparently function to produce a scale of such a character as to 40 retard or eliminate the welding together of pieces of such steel when heated to any temperatures less than the actual fusion temperatures of the same.

So far as is known, this method is the only one 45 permitting the manufacture of sheets of rimmed steel of less than 26 gage. The superior quality of such a product need not be discussed in view of the known qualities of the thicker sheets of such steel. 50

To further define the invention, it might be said that steel of the character being discussed cannot be ordinarily rolled in packs of more than four sheets. The present method permits such steel to be rolled in packs of six or eight sheets, 55

or any other number which practice indicates desirable.

Another advantage in connection with the use of nickel and chromium in the steel is that the objectionable non-metallic inclusions formed by the addition of phosphorus or silicon, as is the usual practice with killed steels, is avoided. These inclusions often cause trouble when the metal is vdrawn deeply, and sometimes even entirely prevent the production of sheets that are commercially perfect.

In view of the fact that there have been :all

sorts of steels made, accidentally or otherwise, it should be understood that the present invention is particularly characterized in that the stated percentages of nickel and/or chromium are deliberately added to rimmed steel for the ultimate purpose of permitting the rolling of this steel into thin sheets, such as 26 gage and. under. This means that it is introduced for the specific purpose of facilitating opening of hot-rolled sheetpacks. So far as 'is known, no one has ever produced a steel of this character for this purpose and with this function in mind. 7

Throughout this specification it has been taken for granted that the reader will understand that the steel used will be of a suitable sheet-bar composition, and that this composition may be conventional except for the addition of the metals mentioned. Also, that the sheet produced will have the physical characteristics of sheet and tin plate excepting for the improvement incidental to the use of rimmed steel. Because of its conventiona'lity, the exact composition of sheet-ba said steel in packs to a thickness of less than '26 gage- 2. A method of facilitating the opening of sheet-packs hot-rolled from rimmed steel, of a suitable sheet-bar composition, with at least six sheets to a pack, including adding from 0.05 to 0.15 percent nickel to said steel while it isin a molten condition.

3. A method of facilitating the opening of sheet-packs hot-rolled from rimmed steel of a suitable sheet-bar composition, with at least six sheets to a pack, including adding from 0.02 to 0.10 per cent chromium to said steel while it is in a molten condition.

. 4. Amethod of producing sheets of a thickness less than 26 gage of rimmed steel of a suitable 10 sheet-bar composition which consists in adding to the molten steel from .05 to .15 per cent nickel, pouring the molten steel while it is still effervescing and hot rolling it in packs.

5. A method of producing sheets of a thickness less than '26 gage of rimmed steel of a suitable sheet-bar composition which consists in adding to the molten steel from .05 to .15 per cent nickel and .02 to .10 per cent chromium, pouring the molten steel while it is still efiervescing and hot rolling it in packs.

6. A method of producing sheets of a thickness less than 26 gage of rimming steel which consists in adding to the :molten steel from .02 to .10 per cent chromium, pouring the molten steel while it is still eiiervescing and hot rolling it in packs.

A method of producing steel in the form of sheets, including producing rimmed steel cf5a suitable sheet-bar composition and containingfron1 0402 to 0.10 .per cent chromium, and hot- 30 working said steel in packs to a thickness of less than 26 gage. V

-;8. A method of producing steel in the form of thin sheets, including producing rimmed steel of a suitable sheet-bar composition and containing from 0.05 to 0.15 percent nickel and from 0.02 to 0. 10 per cent chromium, and hot-working said steel in packs to a thickness of less than 26 gage.

9. A method of facilitating the operation of sheet-packs hot-rolled from rimmed steel of a suitable sheet-bar composition, with at least six sheets to a pack, including adding from 0.05 to 0.1 5 percent nickel and from 0.02 to 0.10 per cent chromium to said steel while it is in a molten condition.

ALBERT T. REICHENBACI-I. 

